Interference is a key technical problem that needs to be resolved by wireless and microwave communications devices. One of main interference of the wireless and microwave communications devices is caused by coupling of a local transmit antenna to a local receive antenna. In order to resolve interference brought by the coupling, an interference cancellation technology may be used: Acquiring a transmit signal from a local transmit end by means of coupling, so as to enable the transmit signal to pass through a simulated interference channel, adjusting a phase of the transmit signal so that a difference between the phase of the transmit signal and a phase of an interfering signal is an odd number times 180°, and then, performing coupling to connect the transmit signal to a local receive end, to cancel the interfering signal.
In an cross polarization interference cancellation (XPIC) system established by using outdoor unit (ODU), because polarization directions of ODUs are different, interference received by each ODU includes co-polarization interference brought by a transmit link of the ODU, and further includes cross polarization interference brought by a transmit link of another ODU. When an interference cancellation technology is used to cancel interference that exists in the XPIC system, each ODU needs at least two reference signals: One reference signal is from the ODU and used to cancel the co-polarization interference; and the other reference signal is from another ODU and used to cancel the cross polarization interference.
In a process of implementing the interference cancellation technology, the inventor finds that the prior art has at least the following problems: In an XPIC system established by using two ODUs having different polarization directions, each ODU needs at least two interference cancellation links; therefore, the established XPIC system is relatively complex.